Two-Cavity Surface-Emitting Laser With Integrated Pump Cavity
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Solution Overview
Problem
Conventional VCSELs have limited output powers due to their small dimensions and require either external optical pumping, which is complex, or electrical pumping, which is inefficient, and they suffer from high divergence and poor beam quality.
Innovation Solution
A TCSEL with a strip-shaped active medium and integrated horizontal pump cavity using Bragg reflectors, allowing for efficient optical pumping and improved beam quality by combining vertical and horizontal cavities, enabling higher output powers and scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the radiating surface of VCSEL is increased to achieve higher output powers, then the output power increases, but the device becomes difficult to electrically pump
Solution Approach 1:
The patent introduces an intermediary pump laser system that optically pumps the VCSEL active region. Instead of directly electrically pumping a large-area VCSEL, a separate pump laser (with wavelength matching the absorption band of the active medium) is used to provide optical pumping, which then generates laser radiation at the desired wavelength. This mediator approach enables high-power operation without the complexity of electrical pumping for large areas.
Solution Approach 2:
The patent merges the pump laser cavity and VCSEL cavity into a single integrated structure. The pump laser and VCSEL share common optical components and the active medium, allowing the pump laser to efficiently couple energy into the VCSEL mode. This merging reduces overall system complexity while enabling high output power through optical pumping.
2Power
If conventional VCSELs use external optical pumping to achieve higher powers, then output power increases, but the device complexity and quantum defects increase
Solution Approach 1:
The patent combines the pump laser cavity and VCSEL cavity into a single integrated structure where the pump laser is formed within the same device as the VCSEL. The pump laser cavity uses the same active medium and shares optical components with the VCSEL, eliminating the need for separate external pump lasers and complex alignment systems.
Solution Approach 2:
The device uses itself as the pump source - the VCSEL structure contains an integrated pump laser that automatically provides the necessary optical pumping. The pump laser is electrically pumped and generates radiation that directly pumps the VCSEL active region, creating a self-contained system that eliminates external pumping complexity.
3Power
If the radiating area is increased for higher power, then output power increases, but the beam quality and symmetry deteriorate
Solution Approach 1:
The patent employs local quality by creating laterally varying properties in the active medium and waveguide structure. The refractive index profile and active region characteristics are optimized at different lateral positions to maintain beam quality across the expanded radiating area. This allows different regions of the device to contribute differently to the overall beam output, preserving symmetry and quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The TCSEL achieves higher output powers, better beam quality, and scalability with simpler pump geometry and reduced quantum defects, while maintaining low divergence and efficient operation.
Implementation Method 1
a first reflector and a second reflector having a high reflection in the wavelength range of the first wavelength... a third reflector and a fourth reflector having a reflection maximum in the range of a second wavelength
Implementation Method 2
with which stimulated emission can be generated in a wide wavelength range, specifically at a first wavelength (laser wavelength) and a second wavelength (pump wavelength)
Implementation Method 3
an active medium - usually with one or more quantum well structures - for the generation of the Laser light
Data Source
Figure 1
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AI summary
The laser has a Bragg-reflector (18) lying opposite to another Bragg-reflector (20). The reflectors exhibit maximum reflection in a range of wavelength. A third Bragg-reflector (12) and a fourth Bragg-reflector (13) are arranged laterally over or adjacent to a strip-like active medium (10). The third reflector lies opposite to the fourth reflector. The third reflector and the fourth reflector exhibit maximum reflection in a range of another wavelength, where the former wavelength is larger than the latter wavelength. The medium is provided with maximum emission at the former wavelength.